The present invention relates generally to special feature systems for an electronic private automatic branch exchange and more particularly to a trunk consultation feature for an electronic private automatic branch exchange which is built around a space divided solid state matrix.
Electronic private automatic branch exchanges are known in the art to provide circuitry for establishing audio paths between PABX stations or between central office trunks and PABX stations. These connections are usually accomplished through the use of a common control which directs the path finding and supervisory functions of a space divided crosspoint matrix on which the PABX station lines and central office trunk circuits appear. Normally, once a path is found between two appearances of the matrix, a sleeve lead is energized to hold the crosspoints of the matrix establishing the connection.
In addition to the normal control of connections between two PABX stations or a central office trunk and a PABX station, it is desirable in private automatic branch exchanges to provide certain special features to add to the flexibility of the exchange and provide additional enhancements desired by the customers. One such special feature that is useful and has gained customer acceptance in many PABX applications is that of trunk transfer.
The trunk transfer feature allows a PABX station (hereinafter called the "transferring station") which is connected to an established incoming or outgoing trunk call (hereinafter called the "transferred party") to hold the connection to the transferred party while signaling the common control to establish a connection to a PABX station (hereinafter called the "transferee station") and then to connect the transferred party to the transferee PABX station. Thus, an incoming trunk caller reaching the wrong PABX station or wishing to talk with an individual at another PABX station after a first connection to a local station may be transferred to the desired transferee PABX station without having to redial. Similarly, a party connected to the PABX via an outgoing trunk may wish to talk to another PABX station after the first connection is completed and may be transferred without dialing.
A novel and advantageous circuit for performing the special feature of trunk transfer in an electronic private automatic branch exchange is described in the application cross-referenced above. In addition to the trunk transfer feature, another useful special feature that may be incorporated into a PABX system is trunk consultation. The trunk consultation feature provides an arrangement to allow a PABX station (hereinafter called the "consulting party") to hold a connected trunk party while establishing a connection to a second trunk party (hereinafter called the "consulted party"). After consultation with the second trunk party, the consulting party usually returns to the original call and the consulted party is released.
In the electronic private automatic branch exchange described, many of the operations performed by the trunk transfer feature can be used additionally to perform similar functions in the trunk consultation operation.